This invention relates to an exhaust system for a personal watercraft and more particularly to a catalytic exhaust system for such watercraft.
There is a very popular and growing segment of the watercraft market for a type of watercraft called a "personal watercraft." This type of watercraft is comprised of a relatively small hull that defines a rider's area which is designed primarily to accommodate a rider and possibly one or two additional passengers. This type of watercraft is generally quite sporting in nature, and the watercraft may at times become inverted or at least partially capsized. In addition, it is frequently the situation that the rider and/or passengers may enter the watercraft from the body of water in which the watercraft is operating. Therefore, it is common for the rider and passengers to wear swimming suits when operating this type of watercraft.
Frequently, this type of watercraft is powered by a jet propulsion unit which is mounted in a tunnel to the underside of the hull, and thus the watercraft provides a very neat and compact appearance. The propulsion unit is frequently a two-cycle internal combustion engine because of the small size and high output of these engines.
As is well known with many types of watercraft, the exhaust gases from the watercraft engine are discharged to the atmosphere either through or close to the body of water in which the watercraft is operating. Thus, environmental concerns raise a desire to ensure that the exhaust gases are relatively clean so as to avoid pollution of not only the atmosphere, but also of the water body. These problems are particularly acute in connection with two-cycle engines because of the fact that frequently the exhaust products contain lubricant and other hydrocarbons.
It is, therefore, a principal object of this invention to provide an improved exhaust system for this type of watercraft.
It is a further object of this invention to provide an exhaust system for a personal watercraft wherein a catalyst is provided in the exhaust system for treating the exhaust gases and removing objectionable exhaust gas constituents.
From the foregoing description it should be readily apparent that the sporting nature of this type of watercraft means that water can, from time to time, enter the exhaust system. This is particularly true when the watercraft is operating with its discharge either at or below the water level. The problem becomes particularly acute in the event the watercraft becomes inverted and is subsequently righted.
As is well known, catalysts operate at a relatively high temperature in order to become efficient. If a large body of water is permitted to come into contact with the catalyst, for example, during the capsizing and righting operation aforenoted, the catalyst bed may become shattered. Even if the bed does not shatter, the water contacting it may cause pollution of the catalyst, particularly when operating in marine environments.
It is a further object of this invention to provide an improved catalytic exhaust system for a personal watercraft wherein the catalyst is positioned so that it will be protected from damage by water.
In addition to the problems of possible water damage or water contamination, the temperature at which the catalyst operates makes it desirable to ensure some arrangement for protecting the surrounding environment in the hull from the heat of the catalyst. This is particularly important with small personal watercraft because of the fact that the engine compartment is relatively small and also because of the fact that the size of the watercraft requires the various components and auxiliaries to be placed close to each other.
It is, therefore, a still further object of this invention to provide an improved arrangement for protecting the surroundings in a personal watercraft from the heat of a catalyst in its exhaust system.
Frequently, it is the practice to encircle at least a portion of the exhaust system such as the exhaust manifold and/or expansion chamber with a cooling jacket through which engine coolant is circulated. This helps not only to silence the exhaust gases, but also to offer protection to the surrounding environment. The water which has passed through the cooling jacket is then generally dumped back into the exhaust system so as to further cool it and to assist in its discharge back to the body of water in which the watercraft is operating. This added water to the exhaust system gives a rise to possible damage to the catalyst, for reasons noted above.
It is, therefore, a still further object of this invention to provide an improved exhaust system for a personal watercraft wherein the exhaust system is provided with a cooling jacket and water is returned from this cooling jacket to the exhaust system but in a way so as to protect a catalyst in the exhaust system from damage.
It is a further object of this invention to provide an improved catalytic exhaust system for a personal watercraft wherein the catalyst is positioned in such a way that it can be easily cooled.
It is a still further object of this invention to provide an improved catalytic exhaust system for a personal watercraft wherein the catalyst is disposed so that it is spaced from other components or auxiliaries of the engine which might be prone to damage from heat.
As has been previously noted, one problem attendant with the provision of catalytic exhaust systems for personal watercraft is the danger of water damage. As has been previously noted, this type of watercraft may become inverted or partially capsized, and upon this condition or upon subsequent righting there is a danger that the water may come into contact with the catalyst.
It is, therefore, a still further object of this invention to provide an improved catalytic exhaust system for a personal watercraft wherein the catalyst and exhaust system is arranged in such a way that the catalyst will always be at a high point, regardless of the orientation of the watercraft, so as to reduce the likelihood of water reaching it.
Although it is desirable to protect the catalyst from contact with water when the engine is running, there may be sometimes when it is desirable to be able to flush the catalyst bed with clear water for cleaning purposes. That is, although the catalyst should not contact the water when the catalyst is at a high temperature and the water is at a lower temperature, there may be containments that are deposited on the catalyst bed. It may be desirable to employ a water flushing arrangement for clearing these contaminants from the catalyst bed.
For example, if the watercraft is operating in a marine environment, the presence of water or water vapor in the exhaust system can give rise to the condensation or deposition of the water born contaminants such as salt on the catalyst bed. Once the watercraft is taken out of operation, it may be desirable to have an arrangement wherein the catalyst bed may be flushed with pure water to remove these deposited contaminants.
It is, therefore, a still further object of this invention to provide an improved arrangement for flushing the catalyst in a watercraft exhaust system.